Ally McCoist's side will be presented with the League One silverware after their clash with Stranraer this afternoon.
The Gers have breezed through the bottom two tiers and Foster reckons they can handle the step up in class next time out.
He said: "I'm not going to sit here and say over the course of a season we could match the teams in the top division - we haven't played enough of them to know if we could.
"But in that one-off game, although we ended up getting beaten 3-1 (to Dundee United), I think we did enough to show that we created chances and had we taken our chances before they took theirs, it could have been a different outcome.
"It was almost bittersweet because although it was horrible to lose a Scottish Cup semi-final, you kind of look back now and realise that although they are a really good team with good players, for a lot of the game we did match them.
"I don't know if we need much change, we just need to get better ourselves.
"The league will be different, the teams will be fitter and they will be better technically and we'll just need to cope with that. We'll get a good pre-season unedr our belts and I would still imagine we'll be one of the fittest teams in the league.
"Although they will be better, I don't think the difference between League One and the Championship will be that great."