As the new High Representative for Foreign Affairs she is to control the planned new EU diplomatic service, which will have a staff of up to 5,000.
The Lisbon Treaty has provided a "once in a generation opportunity" to create "one coherent strategy" for EU foreign policy, she said.
MEPs have the power to veto the whole Commission. The vote is on 26 January.
The European Parliament is the EU's only directly elected institution and has gained greater legislative powers under the Lisbon Treaty.
Each commissioner-designate faces a three-hour grilling by the parliament committee that covers their area. The whole process is set to last a week.
The BBC's Europe correspondent Jonny Dymond says Baroness Ashton concentrated on process rather than any grand new statements of policy.
Iran, Afghanistan, Israel and the Palestinian territories all came up for discussion, as did relations with Russia, North Africa and North Korea.
The commissioners lead the powerful EU civil service for five-year terms. They have the job of drafting new legislation and ensuring compliance with existing legislation, as well as acting as guardians of the EU treaty obligations.
In 2004, MEPs blocked the appointment of Rocco Buttiglione, Italy's nominee for the post of EU justice commissioner, meaning that the proposed Commission team had to be refashioned. MEPs objected to Mr Buttiglione's opposition to gay rights.
Baroness Ashton is among nine women in the new 27-member Commission. She would be a Commission vice-president as well as EU foreign affairs chief.
Each member state has a commissioner, but their role is to act in the common European interest, not to pursue a national agenda.
Baroness Ashton's job was created by the Lisbon Treaty, which went into effect on 1 December, following eight years of difficult negotiations.
The nominees have had some extra time to prepare for the hearings, because of the delay in putting Lisbon into effect.
Finland's Olli Rehn also comes under scrutiny on Monday. Formerly enlargement commissioner, he is the nominee for the economic and monetary affairs portfolio - a sensitive post as Europe's economies struggle to revive growth.
Some nominees are likely to face particularly tough questioning, correspondents say, including Rumiana Jeleva from Bulgaria, the commissioner-designate for international aid and development, and France's Michel Barnier, internal market commissioner-designate.
Among the foreign policy areas covered by Baroness Ashton in her answers were:
Afghanistan - the EU has "huge potential" to "add value" on the ground, she said, including primary healthcare and even providing local police with enough telephones;
Bosnia-Hercegovina - the hope of EU membership is the "glue" that holds the country together, but the EU needs to "reach beyond the political leaders, much more into where the people are and explain to them the benefits";
Union for the Mediterranean - It has had "a difficult year", she said, voicing her readiness to "make it as effective as it should be".
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.