Create flash cards with pairs of opposites. For instance, make one card that shows an open window and one that shows a closed window. Make cards for as many pairs of opposites as you can think of. Spread the cards out and ask preschoolers to match them back up into pairs. To add a memory challenge, spread the cards out picture-side down. Taking turns, each child turns over two cards. If they aren't a pair, he turns them back over and the next child takes a turn. Play until all the matches are found.
Play an opposites version of the game "Simon Says." Gather the children in a group. When you give a command, children must do the opposite. For instance, when you say "Put your arm in front of you," they should put their arms behind them instead. When you say "Be very still," they should jump and wiggle around. Don't include the command "Simon says" since this will only confuse children. A child is out when she forgets to do the opposite of your command.
Compile a list of opposite pairs with the class. Choose words that be found outdoors, such as big versus small and hard versus soft. Take children outside along with a camera and notebooks. Read out one pair of opposites and ask each child to find examples of one of the words. When you call out hard and soft, one child may find a large rock while another finds a patch of soft dandelions. Ask children to draw pictures of what they've found, then take pictures of each child standing next to their examples. Hang the pictures up on an opposites bulletin board.
Children can learn about opposites and practice writing and spelling at the same time. Print off the "Label the Pictures" opposite worksheet from Learning Resources or create your own. Write a word bank of opposite words at the top of the page, then add a clip art picture that demonstrates each word. Add a blank line beneath each picture. Read the words to children, then ask them to write the corresponding word under each picture. Younger preschoolers may need teachers to help them find the correct word.