\oval(width,height)[portion]
The \oval command produces a rectangle with rounded corners. The
optional argument, [portion], allows you to select part of the
oval.
t - Selects the top portion
b - Selects the bottom portion
r - Selects the right portion
l - Selects the left portion
Note that the "corners" of the oval are made with quarter circles with a maximum radius of 20 pt, so large "ovals" will look more like boxes with rounded corners.