An update on manufacturing activity and new-home sales data due Tuesday morning were also in the spotlight.
Futures for the Dow Jones Industrial Average gained 48 points, or 0.3%, to 18,566, while those for the S&P 500 index added 5.60 points, or 0.6%, to 2,187. Futures for the Nasdaq-100 index climbed 13.25 points, or 0.3%, to 4,825.
The implied gains follow lackluster action on Monday, when the mood turned cautious as oil prices tumbled. Hopes faded that members of the Organization of the Petroleum Exporting Countries will agree on a production freeze deal next month.
Investors also were playing a waiting game ahead of a retreat of Fed central bankers and economists at Jackson Hole, Wyo., on Friday, where Yellen will be watched for hints about U.S. monetary policy.
"We could continue to see an element of caution in the markets in the lead up to this. Investors are still not buying a 2016 rate hike, even following [Fed Vice Chairman] Stanley Fischer's comments over the weekend regarding the economy," said Craig Erlam, senior market analyst at Oanda, in a note. On Sunday, speaking at a conference sponsored by The Aspen Institute, Fischer said the central bank is within reach of its twin goals of inflation of about 2% and healthy employment.
"The only question is whether [Yellen will] strongly hint at a hike this year or indicate that holding off to early next year may be warranted, at which point markets would push the hike right back once again," he added.
The market is pricing in a 15% probability of a rate increase in September and a 48.1% chance of it happening in December, according to CME's Fed Watch Too.